Light that falls on a surface can either be absorbed, transmitted or reflected, depending on the properties of the material involved. Reflection factors (r), absorption factors (a) and transmission factors (t) can be between 0 and 1 (0 -100%). The sum of the three factor is always 1. The transmitted or reflected radiation can be regular (1), scattered (2) or completely diffuse (3).


Absorption factor α


The absorption factor is the ratio of absorbed light to incident light. A matt black solid absorbs almost all incident light, while a white solid absorbs very little. Here are some typical absorption factors:

Material

clear glass

2 ... 4%

prismatic glass

5 ... 10%

plastic (white, opaque)

10 ... 20%


Reflection factor ρ


The reflection factor is the ratio of reflected light to incident light. Here are some typical reflection factors:

Material

clear glass

6 ... 8%

prismatic glass

5 ... 20%

plaster

70 ... 80%

Zbrick, red, new

10 ... 15%

cement/concrete, untreated

20 ... 30%

wood, light

30 ... 60%

wood, dark

10 ... 15%

Transmission factor τ


The transmission factor is the ratio of transmitted light to incident light. Here are some typical transmission factors :

Material

clear glass

90 ...92%

prismatic glass

70 ...90%

plastic (white, opaque)

40 ...60%